1. Field of the Invention
The invention relates in general to an antenna structure, and more particularly to an antenna structure having a filter.
2. Description of the Related Art
Today people lay much stress on life technology, and thus are more and more focusing attention to how to effectively enhance convenience of human lives. The good or bad in antenna structure design affects directly transmission and reception of wireless signals. Therefore, how to design an antenna structure of good quality has become an essential subject for wireless technology.
FIG. 1 is a schematic diagram of the conventional antenna structure. The antenna structure 100, such as a detachable antenna, is electrically coupled to an electronic device (not shown in the figure) of a wireless station. The antenna structure 100 includes an antenna unit 110 and a signal transmission line 120. The antenna unit 110, such as formed on a printed circuit board, includes a signal feed-in point 130 and a radiation body 150. The signal transmission line 120 has one end electrically coupled to the signal feed-in point 130 of the antenna unit 110 and the other end coupled connected to a plug 122 and the electronic device. The radiation part 150 is electrically coupled to the signal feed-in point 130.
The conventional antenna of the above-mentioned structure has a gain about 2 dBi. Besides, owing that the electronic device usually has more than one frequency band, for example, a wireless station capable of receiving signals having frequency 2.3 G˜2.6 G or 4.9 G˜6 G, an electronic device usually requires more than one antenna structure 100 for transmitting or receiving wireless signals in different frequency bands. However, an electronic device having more than one antenna structure 100 of different frequency bands will easily cause an electro-magnetic coupling effect and wireless signals of different bands will thus interfere with each other.
In order to prevent the above-mentioned electronic device having the antenna structure 100 of different frequency bands from causing the electromagnetic coupling effect, a filter is usually disposed on the printed circuit board of the electronic device and coupled to the antenna structure 100. However, disposition of the filter will enlarge the printed circuit board of the electronic device and thus increase its manufacturing cost.